Glass breakage alarm systems generally are of two different types, namely, those which respond to mechanical vibrations imparted to the glass upon breakage and those which respond to audio frequency signals which are generated upon breakage. The latter systems are becoming more prevalent because only a single audio detector is required for a room having multiple windows, while the former systems require multiple detectors in a room, one at each window or window section which is likely to suffer glass breakage for entry therein.
Audio signal responsive systems normally utilize a suitable transducer pick-up device, e.g., a microphone, which responds to the audio signal generated by glass breakage and produces an audio frequency electrical signal containing many signal components over the audio portion of the frequency spectrum. Usually such signal is suitably filtered, normally using a single bandpass filter providing a filtered output signal within a selected range of audio frequencies or sometimes using a pair of bandpass filters, one operating over a relatively high frequency band and the other operating over a relatively low frequency band. The filtered output, or outputs, thereof, are suitably processed, e.g., using discrete logic electronic circuitry, to provide an alarm signal at a remote alarm control panel, for example, to produce an appropriate alarm indication thereat, e.g., an audible or visual indication, or both. Typically, for example, the detector system uses an alarm output relay which is normally activated, the relay being de-activated when an alarm condition occurs, thereby interrupting current flow through a circuit loop from the alarm control panel through one or more detectors interconnected with the control panel, as would be well known to the art. Interruptions of such current flow causes an audible and/or a visual alarm indicator to be activated.
Such systems normally obtain their operating supply voltage, e.g., a 12 volt, D-C supply voltage, from power supply circuitry in the alarm control panel, which includes a power voltage filter and voltage regulator to supply a regulated low voltage for operating the circuitry used in the system. If, unknown to the user, the low voltage input to the system is no longer available or drops below a usable low level, the alarm relay may drop out (i.e., become de-activated), thereby producing an alarm condition when no glass breakage has been detected. However, the user cannot tell whether there is a true alarm condition or whether there is a power related failure or whether some other problem has arisen. Such problem arises particularly when many detectors are supplied off the same wire and the number of detectors and the length of the wire tends to cause the input power voltage level at a particular detector to become marginal. In such circumstances it is difficult to troubleshoot the problem of having a detector trip an alarm condition for no apparent reason. It is desirable to be able to provide a user with information when such problem occurs because of a drop in power input voltage below a particular required level.
Moreover, such systems can fail by purposeful compromise thereof, as by blocking out the audio signals normally received by the system, e.g., the microphone sensor can be blocked out to render the sensor useless and, hence, the system fails to detect glass breakage as desired. Since such systems are of a passive nature, if audio input signal blockage occurs in currently available systems, such failure will normally go undetected.
Further, currently available systems require the use of suitably designed electronic equipment for generating specialized electrical signals in order to test the operation of the system and the components therein. Since system users do not normally have such equipment available to them, or do not have the skills for using such equipment, they must now arrange for costly on-site testing operations to be performed by skilled equipment operators. For that reason, users often fail to test the system frequently enough to determine its operability and may forego testing at all for long periods of time.
Further, in order to place the system in a test mode, rather than in an operating mode, for such testing operations, the equipment operator normally must have physical access to the circuitry within the alarm system housing in order to physically alter a component therein, e.g., in order to actuate a switch, to supply an appropriate jumper connection, or the like, for placing the system in a desired test mode.
Moreover, current systems utilize one or more light indicators, e.g., light-emitting diodes (LEDs), often merely for indicating when power to the system has been turned on or off and when the system has responded to an alarm condition, for example. Indication of other operating conditions are usually not provided, although it is often desirable to provide indications of other operating or operating failure conditions. At the same time it is desired that a minimum number of indicator lights be used for such purpose in order to keep the number of components and the cost of the system to reasonable levels.
Finally, currently available audio detection alarm systems normally operate independently of other alarm devices or systems. However, it would be desirable for an audio detection system to be adapted for monitoring another type of alarm device that may be used in conjunction therewith so that the operation of the other device can be suitably monitored so as to confirm the occurance of an intrusion event within a selected time period.